1. Field of the Invention
This invention relates to calcining of delayed petroleum coke in an internally-fired vertical shaft kiln.
2. Description of the Prior Art
Delayed petroleum coke is generally calcined at high temperatures to drive off volatile hydrocarbons and moisture. The calcined product may be used to produce anodes for aluminum manufacture, and in cases where the delayed coke is of a premium quality, it can be used for manufacture of graphite electrodes useful in the electric arc steel making process. Most present-day commercial coke calciners are rotary kilns. Inclined rotary kilns and their operation are described in U.S. Pat. Nos. 4,022,569 and 4,053,365. Another rotary kiln for calcining coke is shown in U.S. Pat. No. 3,759,795.
Vertical shaft kilns have been used for calcining coke. In U.S. Pat. No. 4,251,323 delayed petroleum coke is calcined in an internally-fired vertical shaft kiln. A downwardly moving bed of green coke is preheated in the top of the kiln by rising combustion gases then heat soaked at calcining temperatures in the intermediate section of the kiln. The calcined coke is cooled in the lower sections of the kiln by recycled gas moving upwardly from the lower part of the kiln. Partially cooled calcined coke is recovered from the bottom of the kiln. In this process combustion gases, preheat gases and cooling gases all move upwardly through the downwardly moving bed of coke.
It is an object of the present invention to provide an improved method and apparatus for calcining delayed petroleum coke in an internally-fired vertical shaft kiln. More particularly, it is an object to provide such a process and apparatus with an increased calciner capacity.
It is also an object of the present invention to provide a process and apparatus for calcining delayed coke which is more efficient and reduces the number of metal and refractory components which are exposed to high flame temperatures.
Yet another object of the present invention is to provide an improved flow of the solids and gases in the coke bed of the calcining process.